WORLD CLIMATE RESEARCH PROGRAMME CLIVAR Africa Implementation Plan

Africa is a vast continent straddling the equator with roughly equal landmasses in each hemisphere. It forms one of the three major tropical land areas (along with South America and Indonesia-Borneo or the so-called 'maritime continent') and is surrounded by two of the three tropical oceanic basins. Af-rica's unique geographical position leads to an equally substantial role in determining the characteristics of the general circulation of the atmosphere both regionally and globally. Africa is the third largest heat source for the atmosphere (Hartman, 1994) and potentially the second largest at particular times of the annual cycle. The heat source and associated regional circulations exhibit substantial variability on intraseasonal to decadal timescales. There are three major questions that CLIVAR-Africa must address. The first is: I. What are the causes of African Climate variability and how is this related to other parts of the globe? In general, the role of Africa in the global context has received little attention. However there is strong evidence that suggests that Africa does have an important role in the global climate. The significance of the African heat source in the global context cannot be underestimated. Tropical and subtropical heat sources are able to force equatorial waves (e.g. Gill, 1980) and Rossby waves (e.g. Hoskins et al, 1999) which can propagate vast distances interacting with remote regions in the tropics and extratropics. This is likely to have global impacts on intraseasonal to interannual timescales. A clear example of this is the observed strong relationship that exists between the interannual variability of West African rainfall and Atlantic hurricane activity (e.g. Landsea and Gray, 1992). This is usually interpreted in the way the West African heating impacts on the vertical shear in the tropical Atlantic (e.g. Goldenberg and Shapiro, 1996) but may also be related to the easterly waves and squall lines generated over West Af-rica (e.g. Reed et al, 1977). The synoptic details of the tropical African convection in general and their relationship with annual and interannual climate variations requires further investigation. Improved knowledge of the manner in which the African heat sources, the large-scale circulations and the Atlantic and Indian Oceans interact in the development of the key synoptic systems would lead to opportunities for improving predictability of these variations including tropical cyclone variability. The way the tropical heat sources interact is clearly an area that requires more investigation. A clear example of interaction between Africa and …